电容器在充电和放电过程中,充电电流与()成正比。
A.电容器两端电压;
B.电容器两端电压的变量;
C.电容器两端电压的变化率;
D.电容器两端电压大小。
参考答案:C
(本小题满分12分)
已知数列{an}的前n项和Sn=12n-n2,求数列{|an|}的前n项和Tn.
剖析:由Sn=12n-n2知Sn是关于n的无常数项的二次函数(n∈N*),可知{an}为等差数列,求出an,然后再判断哪些项为正,哪些项为负,最后求出Tn.
Michael's new house is like a huge palace, _____ with his old one. [ ]
A. comparing
B. compares
C. to compare
D. compared